use fmt_macros::{Parser, Piece, Position};

use crate::hir::def_id::DefId;
use crate::ty::{self, TyCtxt, GenericParamDefKind};
use crate::util::common::ErrorReported;
use crate::util::nodemap::FxHashMap;

use syntax::ast::{MetaItem, NestedMetaItem};
use syntax::attr;
use syntax::symbol::{Symbol, kw, sym};
use syntax_pos::Span;

use rustc_error_codes::*;

#[derive(Clone, Debug)]
pub struct OnUnimplementedFormatString(Symbol);

#[derive(Debug)]
pub struct OnUnimplementedDirective {
    pub condition: Option<MetaItem>,
    pub subcommands: Vec<OnUnimplementedDirective>,
    pub message: Option<OnUnimplementedFormatString>,
    pub label: Option<OnUnimplementedFormatString>,
    pub note: Option<OnUnimplementedFormatString>,
}

pub struct OnUnimplementedNote {
    pub message: Option<String>,
    pub label: Option<String>,
    pub note: Option<String>,
}

impl OnUnimplementedNote {
    pub fn empty() -> Self {
        OnUnimplementedNote { message: None, label: None, note: None }
    }
}

fn parse_error(
    tcx: TyCtxt<'_>,
    span: Span,
    message: &str,
    label: &str,
    note: Option<&str>,
) -> ErrorReported {
    let mut diag = struct_span_err!(
        tcx.sess, span, E0232, "{}", message);
    diag.span_label(span, label);
    if let Some(note) = note {
        diag.note(note);
    }
    diag.emit();
    ErrorReported
}

impl<'tcx> OnUnimplementedDirective {
    fn parse(
        tcx: TyCtxt<'tcx>,
        trait_def_id: DefId,
        items: &[NestedMetaItem],
        span: Span,
        is_root: bool,
    ) -> Result<Self, ErrorReported> {
        let mut errored = false;
        let mut item_iter = items.iter();

        let condition = if is_root {
            None
        } else {
            let cond = item_iter.next().ok_or_else(||
                parse_error(tcx, span,
                            "empty `on`-clause in `#[rustc_on_unimplemented]`",
                            "empty on-clause here",
                            None)
            )?.meta_item().ok_or_else(||
                parse_error(tcx, span,
                            "invalid `on`-clause in `#[rustc_on_unimplemented]`",
                            "invalid on-clause here",
                            None)
            )?;
            attr::eval_condition(cond, &tcx.sess.parse_sess, &mut |_| true);
            Some(cond.clone())
        };

        let mut message = None;
        let mut label = None;
        let mut note = None;
        let mut subcommands = vec![];
        for item in item_iter {
            if item.check_name(sym::message) && message.is_none() {
                if let Some(message_) = item.value_str() {
                    message = Some(OnUnimplementedFormatString::try_parse(
                        tcx, trait_def_id, message_, span)?);
                    continue;
                }
            } else if item.check_name(sym::label) && label.is_none() {
                if let Some(label_) = item.value_str() {
                    label = Some(OnUnimplementedFormatString::try_parse(
                        tcx, trait_def_id, label_, span)?);
                    continue;
                }
            } else if item.check_name(sym::note) && note.is_none() {
                if let Some(note_) = item.value_str() {
                    note = Some(OnUnimplementedFormatString::try_parse(
                        tcx, trait_def_id, note_, span)?);
                    continue;
                }
            } else if item.check_name(sym::on) && is_root &&
                message.is_none() && label.is_none() && note.is_none()
            {
                if let Some(items) = item.meta_item_list() {
                    if let Ok(subcommand) =
                        Self::parse(tcx, trait_def_id, &items, item.span(), false)
                    {
                        subcommands.push(subcommand);
                    } else {
                        errored = true;
                    }
                    continue
                }
            }

            // nothing found
            parse_error(tcx, item.span(),
                        "this attribute must have a valid value",
                        "expected value here",
                        Some(r#"eg `#[rustc_on_unimplemented(message="foo")]`"#));
        }

        if errored {
            Err(ErrorReported)
        } else {
            Ok(OnUnimplementedDirective { condition, message, label, subcommands, note })
        }
    }

    pub fn of_item(
        tcx: TyCtxt<'tcx>,
        trait_def_id: DefId,
        impl_def_id: DefId,
    ) -> Result<Option<Self>, ErrorReported> {
        let attrs = tcx.get_attrs(impl_def_id);

        let attr = if let Some(item) = attr::find_by_name(&attrs, sym::rustc_on_unimplemented) {
            item
        } else {
            return Ok(None);
        };

        let result = if let Some(items) = attr.meta_item_list() {
            Self::parse(tcx, trait_def_id, &items, attr.span, true).map(Some)
        } else if let Some(value) = attr.value_str() {
            Ok(Some(OnUnimplementedDirective {
                condition: None,
                message: None,
                subcommands: vec![],
                label: Some(OnUnimplementedFormatString::try_parse(
                    tcx, trait_def_id, value, attr.span)?),
                note: None,
            }))
        } else {
            return Err(ErrorReported);
        };
        debug!("of_item({:?}/{:?}) = {:?}", trait_def_id, impl_def_id, result);
        result
    }

    pub fn evaluate(
        &self,
        tcx: TyCtxt<'tcx>,
        trait_ref: ty::TraitRef<'tcx>,
        options: &[(Symbol, Option<String>)],
    ) -> OnUnimplementedNote {
        let mut message = None;
        let mut label = None;
        let mut note = None;
        info!("evaluate({:?}, trait_ref={:?}, options={:?})", self, trait_ref, options);

        for command in self.subcommands.iter().chain(Some(self)).rev() {
            if let Some(ref condition) = command.condition {
                if !attr::eval_condition(condition, &tcx.sess.parse_sess, &mut |c| {
                    c.ident().map_or(false, |ident| {
                        options.contains(&(
                            ident.name,
                            c.value_str().map(|s| s.to_string())
                        ))
                    })
                }) {
                    debug!("evaluate: skipping {:?} due to condition", command);
                    continue
                }
            }
            debug!("evaluate: {:?} succeeded", command);
            if let Some(ref message_) = command.message {
                message = Some(message_.clone());
            }

            if let Some(ref label_) = command.label {
                label = Some(label_.clone());
            }

            if let Some(ref note_) = command.note {
                note = Some(note_.clone());
            }
        }

        let options: FxHashMap<Symbol, String> = options.into_iter()
            .filter_map(|(k, v)| v.as_ref().map(|v| (*k, v.to_owned())))
            .collect();
        OnUnimplementedNote {
            label: label.map(|l| l.format(tcx, trait_ref, &options)),
            message: message.map(|m| m.format(tcx, trait_ref, &options)),
            note: note.map(|n| n.format(tcx, trait_ref, &options)),
        }
    }
}

impl<'tcx> OnUnimplementedFormatString {
    fn try_parse(
        tcx: TyCtxt<'tcx>,
        trait_def_id: DefId,
        from: Symbol,
        err_sp: Span,
    ) -> Result<Self, ErrorReported> {
        let result = OnUnimplementedFormatString(from);
        result.verify(tcx, trait_def_id, err_sp)?;
        Ok(result)
    }

    fn verify(
        &self,
        tcx: TyCtxt<'tcx>,
        trait_def_id: DefId,
        span: Span,
    ) -> Result<(), ErrorReported> {
        let name = tcx.item_name(trait_def_id);
        let generics = tcx.generics_of(trait_def_id);
        let s = self.0.as_str();
        let parser = Parser::new(&s, None, vec![], false);
        let mut result = Ok(());
        for token in parser {
            match token {
                Piece::String(_) => (), // Normal string, no need to check it
                Piece::NextArgument(a) => match a.position {
                    // `{Self}` is allowed
                    Position::ArgumentNamed(s) if s == kw::SelfUpper => (),
                    // `{ThisTraitsName}` is allowed
                    Position::ArgumentNamed(s) if s == name => (),
                    // `{from_method}` is allowed
                    Position::ArgumentNamed(s) if s == sym::from_method => (),
                    // `{from_desugaring}` is allowed
                    Position::ArgumentNamed(s) if s == sym::from_desugaring => (),
                    // `{ItemContext}` is allowed
                    Position::ArgumentNamed(s) if s == sym::item_context => (),
                    // So is `{A}` if A is a type parameter
                    Position::ArgumentNamed(s) => match generics.params.iter().find(|param| {
                        param.name == s
                    }) {
                        Some(_) => (),
                        None => {
                            span_err!(tcx.sess, span, E0230,
                                      "there is no parameter `{}` on trait `{}`", s, name);
                            result = Err(ErrorReported);
                        }
                    },
                    // `{:1}` and `{}` are not to be used
                    Position::ArgumentIs(_) | Position::ArgumentImplicitlyIs(_) => {
                        span_err!(tcx.sess, span, E0231,
                                  "only named substitution parameters are allowed");
                        result = Err(ErrorReported);
                    }
                }
            }
        }

        result
    }

    pub fn format(
        &self,
        tcx: TyCtxt<'tcx>,
        trait_ref: ty::TraitRef<'tcx>,
        options: &FxHashMap<Symbol, String>,
    ) -> String {
        let name = tcx.item_name(trait_ref.def_id);
        let trait_str = tcx.def_path_str(trait_ref.def_id);
        let generics = tcx.generics_of(trait_ref.def_id);
        let generic_map = generics.params.iter().filter_map(|param| {
            let value = match param.kind {
                GenericParamDefKind::Type { .. } |
                GenericParamDefKind::Const => {
                    trait_ref.substs[param.index as usize].to_string()
                },
                GenericParamDefKind::Lifetime => return None
            };
            let name = param.name;
            Some((name, value))
        }).collect::<FxHashMap<Symbol, String>>();
        let empty_string = String::new();

        let s = self.0.as_str();
        let parser = Parser::new(&s, None, vec![], false);
        let item_context = (options.get(&sym::item_context)).unwrap_or(&empty_string);
        parser.map(|p|
            match p {
                Piece::String(s) => s,
                Piece::NextArgument(a) => match a.position {
                    Position::ArgumentNamed(s) => match generic_map.get(&s) {
                        Some(val) => val,
                        None if s == name => {
                            &trait_str
                        }
                        None => {
                            if let Some(val) = options.get(&s) {
                                val
                            } else if s == sym::from_desugaring || s == sym::from_method {
                                // don't break messages using these two arguments incorrectly
                                &empty_string
                            } else if s == sym::item_context {
                                &item_context
                            } else {
                                bug!("broken on_unimplemented {:?} for {:?}: \
                                      no argument matching {:?}",
                                     self.0, trait_ref, s)
                            }
                        }
                    },
                    _ => bug!("broken on_unimplemented {:?} - bad format arg", self.0)
                }
            }
        ).collect()
    }
}
